7812 Voltage Regulator
A DC voltage regulator is a circuit that steps down DC voltage accurately according to need of the circuit. In this article you will learn to step down DC voltage to 12 v. We are going to make a linear voltage regulator circuit using IC 7812.
Components Required
To make 7812 voltage regulator circuit we will need.
- DC supply ( 14 v – 35 v ), 1 A
- 7812 IC
- 100 µF / 36 V capacitor
- 10 µF / 16 V capacitor
- Breadboard or VERO board
- Wires / Soldering iron
7812 Voltage Regulator Circuit
Tutorial
Follow these steps to make your connection for 7812 –
- First of all place 7812 IC on breadboard / VERO board.
- Connect pin number 1 of IC to positive input supply. Suppose 15v 0.5 A.
- Connect the negative input supply to pin number 2.
- Put 100 µF capacitor between the terminals 1 and 2.
- Put 10 µF capacitor between the terminals 2 and 3.
- Attach positive terminal of multi-meter / voltmeter to pin number 3 ( output positive pin ).
- Attach negative terminal of multi-meter / voltmeter to pin number 2 ( output negative pin ).
- Turn on the supply and the meter will measure 12v.
Working
7812 is a voltage regulator IC that provides 12 v output when an input voltage of 14 v – 35 v is provided. The DC input is applied to pin number 1 and 2 and the output DC voltage is obtained from pin 2 and 3. Where pin 2 is common for negative terminal as shown in circuit diagram.
For constant use of the IC, input voltage should not exceed 28v.
Linear voltage regulator drop voltage and emit ( looses ) them in the form of heat.
Advantage of 7812 Voltage Regulator
The advantages of 7812 IC are –
- Simple circuit, easy to make only few components are required.
- Cheap
- Accurate output voltage
- High temperature tolerance
Disadvantages
The disadvantages of 7812 IC are –
- Requires heat sink. Power is lost ( emitted ) in the form of heat.
- Linear voltage regulator has low efficiency.
Power Loss in 7812
We have already discussed above that 7812 circuit is a linear voltage regulators. They drop power and losses ( emit ) them in the form of heat.
Suppose we provide 15v 0.5 A input to 7812 IC that has an output of 12 v 0.5 A.
So the voltage drop made by IC will be 3 v.
We know,
Power (P) = Voltage ( V ) x Current ( I )
Power loss = 3 x 0.5 = 1.5 W
Input power = 15 x 0.5 = 7.5 W
Power output = 12 x 0.5 = 6 W
The 6 W power loss heats up metal back of 7812 IC. Here we attach heat sink.
On an average there is 20° C rise in temperature of IC per watt loss.
1.5 W can raise up-to 1.5 x 20 = 30° C
If we take 27° C as normal temperature of 7812 IC then the IC can heat up-to 27° + 30° C = 57° C. According to manufacturers the IC can tolerate maximum 125° C. 57° C is still too high.
In this case we must use a good aluminium heat sink. This heat sink needs to be attached properly to the back side if IC that gets heated. There is a hole on top of IC where you can pass a screw or a bolt through it in-to heatsink and attach both of them using nut.
Cautions
Although 7812 IC is a simple and cheap solution for the circuits. You always be careful while using it.
Make sure the input current / voltage should not go above the current / voltage rating of IC. It can easily blow up.
Connect input and output pins of IC carefully. Reverse connection can damage the IC.
Author
Akash Sharma
